A motor drive control circuit includes a rotation control amplifier that
compares the lower of a voltage limiting reference voltage of a reference
voltage source and a rotation speed control voltage, which controls the
rotation speed of the motor, on a terminal with a peak voltage from an
impedance element that detects a drive current of a motor. The motor
drive control circuit further includes a rotation limiting comparator
that compares a voltage that is substantially equal to the voltage
limiting reference voltage with the peak voltage, a synthesis circuit
that amplifies rotation position detection signals from the motor
according to the output voltage of the rotation control amplifier, a PWM
output comparator that compares the outputs of the synthesis circuit with
a triangular wave voltage and outputs PWM signals, and a motor-driver
control circuit that removes an output period of the rotation limiting
comparator from the ON period of each PWM signal and controls a motor
driver that drives the motor. The motor drive control circuit operates
the elements defining the motor driver more in a safe operation region.